The longest-running and most successful sci-fi series in history, "Doctor Who," first introduced its inquisitive, witty time lord on the BBC's airwaves on November 23, 1963. In honor of this milestone, BBC America is going all out with a 50th anniversary special, entitled "Doctor Who: The Day of the Doctor," that will be broadcast simultaneously to more than 75 countries, airing in the U.S. on November 23rd at 2:50pm ET.

The longest-running and most successful sci-fi series in history, "Doctor Who," first introduced its inquisitive, witty time lord on the BBC's airwaves on November 23, 1963. In honor of this milestone, BBC America is going all out with a 50th anniversary special, entitled "Doctor Who: The Day of the Doctor," that will be broadcast simultaneously to more than 75 countries, airing in the U.S. on November 23rd at 2:50pm ET.

The special, which was written by Steven Moffat, will feature exiting Eleventh Doctor Matt Smith and his companion Clara Oswald (Jenna Coleman) as well as appearances by the Tenth Doctor David Tennant, his companion Rose Tyler (Billie Piper) and John Hurt as a "forgotten" incarnation of the Doctor. The official synopsis from the BBC:

The Doctors embark on their greatest adventure in this 50th anniversary special. In 2013, something terrible is awakening in London’s National Gallery; in 1562, a murderous plot is afoot in Elizabethan England; and somewhere in space an ancient battle reaches its devastating conclusion. All of reality is at stake as the Doctor’s own dangerous past comes back to haunt him.

Check out a very brief clip from "The Day of the Doctor" here:

Leading up to the special, the network will also present a week-long "Doctor Who" takeover starting on November 18, with marathons, behind-the-scenes looks and primetime specials devoted to the iconic series. Here's the schedule, with descriptions courtesy of BBC America:

Doctor Who: Tales from the TARDIS, 9:00 –10:00pm ET (U.S. Premiere)An all-new special, Doctor Who: Tales from the TARDIS, features the series’ actors and producers sharing their experiences and memories of the world’s longest-running sci-fi show. The special features exclusive interviews with principal cast members from the show’s 50-year history, including actors who have played the Doctor: Matt Smith, David Tennant, Tom Baker, and Peter Davison, actors who have played companions: Jenna Coleman, Karen Gillan, Freema Agyeman, and William Russell, as well as the current lead writer and executive producer Steven Moffat. The discussion includes how the actors got cast, how the roles changed their lives, how a ‘regeneration’ is recorded, and how filming the show in the 60's compares to today.

The Science of Doctor Who with Brian Cox, 10:00–11:00pm ET (U.S. Premiere)A former rock star and Britain’s popular TV physicist, Professor Brian Cox explores the universe of the world’s favorite Time Lord when he takes the audience on a journey into the wonderful universe of Doctor Who, with the help of celebrity guests. In this exclusively recorded special from the lecture theatre of the Royal Institution of Great Britain, Brian reveals the science behind the spectacle and explains the physics that allows Doctor Who to travel through space and time. Fun, but filled with real science, it’s a special night for Who fans and anyone with a thirst for understanding.

Doctor Who Explained, 8:00pm – 9:00pm ET (U.S. Premiere)An all-new special, Doctor Who Explained, explores the mysterious and two-hearted alien who is the Doctor. Through exclusive interviews with principal cast members from the show’s 50-year history, including actors who have played the Doctor: Matt Smith, David Tennant, Peter Davison, and Tom Baker as well as actors who have played companions: Jenna Coleman, Karen Gillan, and Freema Agyeman, viewers get an insight to what happens behind-the-scenes of the award-winning sci-fi show.

An Adventure in Space and Time, 9:00pm ET (U.S. Premiere)What do you get when you mix C.S. Lewis with H.G. Wells, and sprinkle in a bit of Father Christmas? An alien Time Lord exploring space and time in a Police Box spaceship called the “TARDIS” (Time And Relative Dimension in Space). Written by Mark Gatiss, the BBC AMERICA co-production, the film stars David Bradley (the First Doctor, William Hartnell), Brian Cox (BBC Head of Drama, Sydney Newman), Jessica Raine (Producer, Verity Lambert) and Sacha Dhawan (Director, Waris Hussein). An unlikely trio of misfits set out to create a genre series that all ages would love. William ‘Bill’ Hartnell, displeased with his career, was presented with a chance to break out of the hard-man roles he’d become known for. And with the instincts of first time producer, Verity Lambert and first time director, Waris Hussein, the Doctor was born. As the success of the show grew, William went from unhappy curmudgeon to beloved television star who relished his career resurgence and found a new lease on life. But all good things come to an end. How will Bill face leaving behind the part that has made him a hero to millions of children? And can the show survive without him? Journey back fifty years through space and time to witness the exciting beginning and untimely end of the First Doctor in this touching drama.

Doctor Who: The Day of the Doctor, Global Simulcast – 2:50pm ET (World Premiere)The centerpiece of BBC AMERICA’s celebrations is the global simulcast of Doctor Who’s 50th Anniversary special, Doctor Who: The Day of the Doctor, written by Steven Moffat. The Doctors (Matt Smith and David Tennant) embark on their greatest adventure across space and time. In 2013, something terrible is awakening in London’s National Gallery; in 1562, a murderous plot is afoot in Elizabethan England; and somewhere in space an ancient battle reaches its devastating conclusion. All of reality is at stake as the Doctor’s own dangerous past comes back to haunt him. Starring Matt Smith, David Tennant, Jenna Coleman, with Billie Piper and John Hurt. Last seen as the Doctor on January 1, 2010, this will be the first time David Tennant has reprised his role as the Tenth Doctor. During his reign as the Time Lord, Tennant appeared in three seasons as well as several specials. He was first revealed as the Doctor in the 2005 season finale, The Parting of the Ways. Meanwhile Billie Piper, who played companion Rose Tyler for two seasons following the reboot in 2005, will appear in the show for the first time since featuring in David Tennant’s last episode, The End of Time in 2010. The special is directed by Nick Hurran, executive produced by Steven Moffat, Faith Penhale and produced by Marcus Wilson.

Doctor Who: The Day of the Doctor encore primetime broadcast, 7:00pm ET.BBC AMERICA will premiere exclusive Inside Look interviews with Matt Smith and David Tennant during the broadcast. The special will be followed by the premiere of new fantasy-adventure series Atlantis at 9:00pm ET.

The Graham Norton Show with guests Matt Smith and David Tennant, 10:00pm ET (U.S. Premiere)Doctor Who stars Matt Smith and David Tennant make their first appearance together on BBC AMERICA’s hit talk show The Graham Norton Show. Emma Thompson, singer Robbie Williams and comedian Jimmy Carr will also be guests.

SUNDAY, NOVEMBER 24

Doctor Who – Matt Smith Countdown, 9:00am – 8:00pm ETBBC AMERICA counts down the top 11 episodes from the Eleventh Doctor, Matt Smith, as voted on by fans.

Doctor Who: The Doctors Revisited –The Eleventh Doctor, 8:00pm –10:30pm ET (U.S. Premiere)BBC AMERICA celebrates the Eleventh Doctor, Matt Smith, in a new special of Doctor Who: The Doctors Revisited. Matt Smith first stepped into the TARDIS in 2010 and, after starring in the 50th Anniversary Special on November 23, will regenerate in the Christmas special. The Doctors Revisited begins with Matt Smith, Jenna Coleman (companion Clara Oswald), Karen Gillan (companion Amy Pond), Arthur Darvill (companion Rory Williams), lead writer and executive producer Steven Moffat, among others, examining the human side of this Doctor and taking a look at how his extraordinarily long life has affected him. The special is followed by the Eleventh Doctor two-part story, The Impossible Astronaut and Day of the Moon, in which a strange summons reunites the Doctor, Amy (Karen Gillan), Rory (Arthur Darvill) and River (Alex Kingston) in the middle of the Utah desert and unveils a terrible secret the Doctor's friends must never reveal to him. These were the first Doctor Who episodes to be filmed in the U.S.